It has been known that as an piezoelectric material for an actuator, lead zirconate titanate ceramic composition (PZT) has excellent piezoelectric properties. Various improvements have been made depending on the use. The properties of the piezoelectric material for an actuator have been improved by, for example, a method wherein a part of lead zirconate titanate is substituted with divalent ions such as Ba.sup.2+, Sr.sup.2+ or Ca.sup.2+ or trivalent ions such as Bi.sup.3+ or La.sup.3+, a method wherein an oxide such as NiO, Nb.sub.2 O.sub.5, MnO.sub.2 or Cr.sub.2 O.sub.3 is added, and a method wherein a solid solution with a composite perovskite such as Pb(Zn.sub.1/3 Nb.sub.2/3)O.sub.3, Pb(Co.sub.1/3 Nb.sub.2/3)O.sub.3 or Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 is synthesized. The piezoelectric actuator elements for controlling the fine displacement at a precision of a micron or submicron order include a unimorph type, a bimorph type and a laminated type. Such piezoelectric actuator elements are required to have, as their characteristics, a high piezoelectric strain constant (for example, a piezoelectric strain constant of transversal mode. d.sub.31 &gt; 300.times.10.sup.-12 m/V) and a high Curie point (Tc&gt;150.degree. C.).
In general, in the case of a material having a high piezoelectric strain constant, the Curie point is low. For example, conventionally, in the case of a material having a high piezoelectric strain constant, of which the piezoelectric strain constant of transversal mode exceeds (d.sub.31) 300.times.10.sup.-12 m/V, the Curie point Tc tends to be as low as around 100.degree. C. and the upper limit of the operating temperature of the element is restricted to 50.degree. C. to 60.degree. C., whereby the application as a practical element has been restricted. In the case of a material having a high Curie point, the piezoelectric strain constant tends to be low, and there has been a drawback that high voltage is required to actuate the element. For these reasons, it has been desired to develop a material having a high piezoelectric strain constant, of which the piezoelectric strain constant of transversal mode (d.sub.31) exceeds 300.times.10.sup.-12 m/V, and a high Curie point (for example, Tc&gt;150.degree. C.).